Then it's not being scanned by spamassassin. spamassassin adds headers into the emails. For example, taken from an email I received today:
Code:
X-Spam-Checker-Version: SpamAssassin 3.2.4 (2008-01-01) on mail.[redacted]
X-Spam-Level:
X-Spam-Status: No, score=-1.2 required=5.0 tests=AWL,BAYES_00, HTML_IMAGE_ONLY_24,HTML_MESSAGE,MIME_HTML_ONLY,MIME_HTML_ONLY_MULTI, MPART_ALT_DIFF autolearn=no version=3.2.4
Checking against blacklists isn't really enough to keep your inbox clean. I don't have any experience configuring mailscanner so you'll have to see if anyone else on the board can help you with that.